1. Field of the Invention
The invention relates to processes for hydrogenation of aldehydes to alcohols using certain novel rhodium complexes as homogeneous catalysts.
2. Description of the Prior Art
Hydrogenation of aldehydes to alcohols is an important part of oxo alcohol process. Most oxo alcohol processes use heterogeneous catalysts to accomplish the hydrogenation of aldehydes to alcohols although the aldehydes are produced using homogeneous catalysts. Continuing efforts have been devoted towards improving both the catalysts and processes of the hydrogenation reaction. For example, a) WO2004026800 A1, 20040401, “Process for production of an alcohol by the catalytic hydrogenation of a hydroformylation reaction-produced aldehyde in the presence of an organic sulfur compound” (Brown, Alistair Chalmers Ramsay. Johnson Matthey PLC, UK), described A process for the production of an alcohol (e.g., 3,5,5-trimethylhexanol) by hydrogenation of an aldehyde (e.g., 3,5,5-trimethylhexanal) over a copper and zinc-containing catalyst comprises the step of treating the reduced catalyst with a sulfur compound (e.g., thiophene). The process reduces the hydrogenation of olefin contained in the aldehyde feed compared with a process using an untreated catalyst; and b) CN1275439 A, 20001206, “Preparation and application of liquid-phase hydrogenation catalyst”, (Wang, Xiuling; Li, Dongli; Zhu, Xubo. Beijing Institute of Chemical Engineering, China Petro-Chemical Co., Ltd., Peop. Rep. China), described a new catalyst that contains Ni 5–40, Co 0.2–5.0, Mo 0.2–5.0, Cr 0.5–6, K 0.5–2%, and carrier. The catalyst is prepared by mixing SiO2 or diatomite, water, and binder, forming by extrusion, drying, calcining to obtain carrier, impregnating the carrier in a solution containing the salt of Ni, Co, Cr, K, and Mo, and drying. The catalyst is used in hydrogenation of aldehyde to prepare saturated alcohols.
Although unmodified cobalt catalyst and trialkylphosphine modified cobalt and rhodium catalysts have been used to produce alcohols directly from olefins, only a few oxo alcohol producers operate such “one-step” processes to produce alcohols from olefins. The limited utility of these catalysts is due to low regio- and chemo-selectivity, e.g. high degree of isomerization of alpha-olefins to internal olefins and low linear to branched product selectivity. An earlier patent from Shell, c) DE 1909619, for example, described the use of a phosphine modified cobalt catalyst to convert 1-dodecene (98.5 wt % conversion) to yield unsaturated hydrocarbons (14%), n-tridecanol (50.9%), and branched primary alcohols (33.4%).
There are continued efforts in improving such “one-step” processes. For example: d) WO2004054946 A1, 2004 Jul. 1, “Hydroformylation process for the conversion of an ethylenically unsaturated compound to an alcohol” (Drent, Eit; Suykerbuyk, Jacoba Catherina Lucia Johanna, Shell Internationale Research Maatschappij B.V., Neth.), described a hydroformylation process for the conversion of an ethylenically unsaturated compound to an alcohol comprising a first step of reacting at an elevated temperature in a reactor the ethylenically unsaturated compound, carbon monoxide, hydrogen, and a phosphine-containing cobalt hydroformylation catalyst, which are dissolved in a solvent, followed by a second step of separating a mixture comprising the alcohol and heavy ends from a solution comprising the catalyst and the solvent, followed by a third step of recycling the solution to the reactor; and e) EP 420510 A2, 1991 Apr. 3, “Process for the preparation of alcohols” (Cole-Hamilton, David J.; Macdougall, Joanna K.; Green, Michael James. British Petroleum Co. PLC, UK), described a process comprising reacting an olefin R2CH:CHR1 [R1, R2═H, (substituted) C1-10 alkyl, —C6-12 aryl, C1-10 alkenyl] with CO and optionally H in presence of C1-20 aliphatic alcohol solvent and a catalyst comprising PR3 (R═C1-10 alkyl) and a Rh component, to give an alcohol that has 1 C more than the reactant olefin; f) WO 9739995 A1, 1997 Oct. 30, “Preparation of unsaturated alcohols” (Guram, Anil Sakharam; Briggs, John Robert; Olson, Kurt Damar; Eisenschmid, Thomas Carl; Packett, Diane Lee; Tjaden, Erik Bruce. Union Carbide Chemicals and Plastics Technology Corp., USA), described conversion of 1,3-butadiene to 3- and 4-pentenols in EtOH in the presence of Et3P and dicarbonylacetylacetonatorhodium (I) at 80° C. in a stirred reactor under pressure (300 psi H/300 psi CO); g) GB2306344 A1, 1997 May 7, “Hydroformylation process and catalysts for the preparation of linear alcohols from alpha-olefins”, (Arnoldy, Peter, Shell Internationale Research Maatschappij BV, Neth.), described preparation of linear alcohols (e.g., 1-dodecanol) by the reaction of alpha-olefins (e.g., 1-undecene) with H2 and CO in the presence of catalyst systems comprising: (A) a source of Group VIIIB metal cations (e.g., a palladium salt); (B) a source of anions other than halide ions (e.g., F3CSO3H); (C) a bidentate ligand [e.g., 1,2-bis(1,4-cyclooctylenephosphino)ethane]; and (D) an alkali or alkali-earth metal iodide (e.g., KI);
There is growing interests in developing mixed catalyst systems to convert olefins to alcohols in “one step”. For example, h) WO 2001070660 A1, “Combined hydroformylation and hydrogenation process and catalysts for preparing an alcohol directly from an olefin” (Lange, Jean-Paul, Shell Internationale Research Maatschappij BV, Neth.), described a process for the preparation of an alcohol (e.g., 1-nonanol) from an olefin (e.g., 1-octene) by reacting the olefin with synthesis gas (i.e., H2 and CO) in the presence of a catalyst system comprising a homogeneous hydroformylation catalyst [e.g., palladium acetate and 1,3-bis(dibutylphosphino)propane] and a heterogeneous catalyst comprising copper on a support (e.g., silica); i) U.S. Pat. No. 6,426,437 B1, 2002 Jul. 30, “Hydroformylation and hydrogenation process and catalysts for the manufacture of 1,4-butanediol from allyl alcohol” (Shum, Wilfred P. Arco Chemical Technology, L.P., USA), described preparation of 1,4-Butanediol by hydroformylating allyl alcohol in the presence of a solvent and a catalyst system comprising a rhodium complex, a ruthenium complex, and a diphosphine ligand, and hydrogenating the resulting 4-hydroxybutyraldehyde using the same catalyst system. This process gives high yields of 1,4-butanediol when compared to the 2-methyl-1,3-propanediol byproduct.
There is a need to develop homogeneous aldehyde hydrogenation catalysts that are compatible with more selective hydroformylation catalysts to produce alcohols from olefins in the same reactor under mild low pressure oxo conditions. The most studied homogeneous aldehyde hydrogenation catalysts are ruthenium and rhodium systems. Both ruthenium and rhodium catalysts, however, suffer from the need of very high temperatures and pressures and/or slow rate of hydrogenation. RuC12(CO)2(PPh3)2, for example, was reported (Walter Strohmeier and Luise Weigelt, Journal of Organometallic Chemistry, 145 (1978) 189–194) to hydrogenate butanal with 3840 turnover/hour rate at 160° C. and 15 atmosphere hydrogen. The selectivity to butanol was only 87% due to formation of heavier by-products from aldol condensation reactions. The same catalyst was reported (Sanchez-Delgado, R. A.; Andriollo, A.; De Ochoa, O. L.; Suarez, T.; Valencia, N. Journal of Organometallic Chemistry (1981), 209(1), 77–83) to have a very slow propionaldehyde hydrogenation rate of 67 turnovers/hour at 80° C. and 30 atmosphere of hydrogen, with even lower selectivity (67%) for propanol. In the same article, RuHCl(PPh3)3 was reported to be a much better catalyst for propionaldehyde hydrogenation with a rate of 653 turnovers/hour under the same conditions. Replacing a triphenylphosphine from RuHCl(PPh3)3 with a CO reduced the catalyst activity to about 50%. The most effective rhodium catalysts for aldehyde hydrogenation are rhodium complexes of tri-n-alkylphosphines. A cationic rhodium complex of triethylphosphine, for example, was reported (Fujitsu, Hiroshi; Matsumura, Eiichi; Takeshita, Kenjiro; Mochida, Isao. Journal of Organic Chemistry (1981), 46(26), 5353–7) to hydrogenate n-butanal at 30° C. and one atmosphere hydrogen with a rate of 31 turnovers/hour. Both catalyst systems in EP420510A2 and WO9739995A1 cited hereinabove comprised of aldehyde hydrogenation catalysts although the structures of the catalysts have not been fully identified. Both systems required high temperature and high syn gas pressure to achieve acceptable rate of reactions.